This invention relates to a fluid treatment apparatus for scale removal in circulating fluid systems, and more specifically to an electronic fluid treatment apparatus having parallel metal planar electrodes to modify the electrical charge on any minerals within the fluid.
Circulating fluid systems as for example, water heaters, boilers and heat exchangers using fresh water supplies often encounter a problem with encrustation or scaling due to mineral deposits. Fresh water supplies normally contain a relatively large amount of minerals which separate from the fluid to form a crystallized compound. Since many of the minerals found in this scale have inverted solubility curves, that is their solubility decreases as the temperature rises, hot water circulating systems are especially endangered by scale depositing. The more common minerals that cause economic loss due to scale deposits are calcium and magnesium sulfate and calcium and magnesium carbonate.
There have been many theories propounded concerning scale formation, scale removal and scale control as well as an equal number of devices and methods for treating the same. Electrical devices for treatment of moving fluid have been known for many years and have met with varying success. In theory scale formation proceeds by the deposition of crystalline material about scattered micronuclei as the constituent ions arrange themselves in the growing compound in a definite geometric pattern. The resulting crystal has a definite internal structure and an outward form bounded by charged planes. Scale may form on the surfaces in contact with the water if the atomic particles are allowed to form a latice structure or unit cell which may take on a repetitive three dimension form. The binding forces keeping the crystal in contact are electrostatic between the ions present. Any chemical or electrical device that interferes with the building of the crystalline matrix will prevent formation of an integrated solid deposit of scale, although it will not normally prevent the precipitation of the minerals from the water.
To date methods and devices that have been proposed to solve the scaling problem fall into two categories: chemical and electrical. Chemical treatment has been used for many years to assist in controlling scale in water systems. Certain chemicals such as the molecularly dehydrated phosphates or certain organic substances of the natural or synthetic organic polymer types are able to modify the charges along the faces of the micronuclei and prevent the formation of sufficiently large crystalline structures that would preclude normal heat transfer. Chemical treatment is costly and has been found in some instances to be ineffective. Further, the pollution associated with chemical discharge have provided a demand for new solutions to the problems of scaling in the water systems.
The second category of methods and devices for controlling scaling in water systems, that is, the electrical devices, may be further categorized into electrostatic, electromagnetic, electrophoretic and electronic. All these devices are attempting to interfere with the formation of mineral incrustation by use of electricity.
Electrostatic water treatment devices such as the device disclosed in U.S. Pat. No. 4,073,712, entitled "Electrostatic Water Treatment" by Means et al provide an electrostatic field across an anode and cathode by placing a high voltage across electrodes which are insulated from each other and from the water itself. A limitation in this type of device is in the strict thickness requirement of the insulation used to protect the electrodes from the water. Any increase in size in the anode or cathode of the structure is limited due to the higher voltage requirements and critical insulation thickness on a larger area.
Electromagnetic water treatment devices utilize a permanent or electronmagnet to generate a magnetic field to accomplish a similar result as the electrostatic field described above. A limitation in increasing the size of an electromagnetic water treatment device for greater area exposure is the power requirements to generate the magnetic field which may be 10 amps or more.
An electrophoretic water treatment system utilizes dissimilar metals to simulate a galvanic cell which attracks particles to oppositely charged electrodes.
In an electronic water treatment apparatus, an electric field is generated between oppositely charged electrodes by using a low voltage DC power supply. Further, the electrodes although insulated from each other are not insulated from the fluid itself. An example of an electronic water treating apparatus used in a pressurized water circulating system is manufactured by Hydrotreat, Inc., Houston, Tex., assignee of the present invention. The Hydrotreat water treater consists of a barrel in which the selected electronic signals are introduced into the system and an electronic assembly by which the signals are generated. An electrode at the center of the barrel is in direct electrical contact with the system water and is electrically insulated from the outer cylinder of the barrel. The electronic signals are supplied to the center electrode which serves as the anode. The outer cylinder is also in direct electrical contact with system water and is at electrical ground and serves as the cathode. The water is treated electronically as it flows between the center anode and the outer cathode.
All of the above types of water treatment devices have positive effects on the interference of crystaline formation, which results in precipitation of minerals downstream. However, due to the limitations presented above concerning the electrostatic, the electromagnetic, and electrophoretic devices, greater efficiencies may not be obtained by substantially increasing the surface area of the electrodes used in those systems. Further, in all of the above devices including the electronic device, the inherent problem of installation within the piping system requires shutdown of the circulating water system as well as costly modification of the piping.